Chemical Composition and Mechanical Properties of Seamless Steel Pipe, ASTM A335-P91 Standard
Hit：342026-03-30 11:10:20
Chemical Composition and Mechanical Properties of Seamless Steel Pipe, ASTM A335-P91 Standard
P91 seamless steel pipe is a 9Cr-1Mo martensitic heat-resistant steel conforming to ASTM A335/A335M and ASME SA-335 standards, with the corresponding Chinese national standard designation of 10Cr9Mo1VNbN. It is widely used in critical equipment such as boilers, petrochemical, and nuclear power applications under high-temperature and high-pressure conditions.
Chemical composition (mass fraction %)
Based on a comprehensive review of multiple authoritative public sources, the typical chemical composition range for P91 seamless steel pipes is as follows:
Element Content Range (%)
C (Carbon) 0.08 ~ 0.12
Mn (Manganese) 0.30 ~ 0.60
Si (Silicon) 0.20 ~ 0.50
P (Phosphorus) ≤ 0.020
Sulfur (S) ≤ 0.010
Cr (Chromium) 8.00 ~ 9.50
Mo (Molybdenum) 0.85 ~ 1.05
V (Vanadium) 0.18 ~ 0.25
Nb (niobium) 0.06 ~ 0.10
N (Nitrogen) 0.03 ~ 0.07
Ni (Nickel) ≤ 0.40
Al (aluminum) ≤ 0.04
Others (Ti, Zr, etc.) ≤ 0.01
The listed C ≤ 0.40% is significantly high and inconsistent with mainstream standards and engineering practices. It should be adjusted to 0.08~0.12%, a range consistently adopted by ASTM, ASME, GB/T 5310, and multiple authoritative manufacturers
Mechanical Properties (Room Temperature, Normalized + Tempered Condition)
The typical mechanical properties of P91 seamless steel pipe after treatment with normalization at 1040–1080°C and tempering at 750–780°C are as follows:
Tensile strength (Rm): ≥ 585 MPa
Yield strength (Rp0.2): ≥ 415 MPa
Rearward elongation (A): ≥ 20%
Hardness: Typically ≤ 250 HBW or 25 HRC
Impact energy (KV2): Longitudinal ≥ 40 J, Transverse ≥ 27 J (may vary slightly according to standard and wall thickness)
At a high temperature of 600°C, its yield strength (Rp0.2) remains ≥198 MPa, with a endurance strength approximately twice that of conventional P22 steel, making it suitable for long-term operation in environments ≤625°C
